This invention relates generally to absorbent materials such as those used in making absorbent structures for disposable articles including diapers, children's training pants, feminine care articles, incontinence articles, bandages, surgical gowns, absorbent wipes and the like, and more particularly to such absorbent materials having an enhanced gel bed permeability under load.
Conventional disposable articles typically include an absorbent structure, also sometimes referred to as an absorbent core or absorbent composite, formed by air-forming, air-laying, co-forming, wet-laying or other known forming technique. There is a continuing effort by absorbent structure manufacturers to improve the liquid intake performance of absorbent structures to thereby reduce the tendency of such a structure to leak as it becomes increasingly saturated during use, particularly where the structure is subjected to repeated liquid insults before being discarded. For example, one means of reducing the leakage of absorbent structures has been the extensive use of superabsorbent materials. In addition to increasing the amount of superabsorbent material mass, recent efforts in commercial absorbent structure design have generally focused on using a higher concentration of superabsorbent material and less fiber to make the absorbent structure thinner and denser.
However, notwithstanding the increase in total absorbent capacity obtained by increasing the concentration of superabsorbent material, such absorbent structures may still leak during use. The leakage may in part be the result of the structure having an insufficient intake rate, e.g., the rate at which a liquid insult can be taken into and entrained within the structure for subsequent absorption by the superabsorbent material. More particularly, the intake rate of such absorbent structures may decrease upon repeated insults thereof due to the tendency of the superabsorbent material within the structure to swell as it absorbs and thus restrict or otherwise block the open channels between superabsorbent particles, or between the particles and the hydrophilic fibers within the absorbent structure. This phenomenon is often referred to as a form of gel-blocking and may occur as a result of the superabsorbent material lacking sufficient gel integrity under an external pressure, such as those loads applied by a wearer during movement or upon sitting down.
The ability to maintain openness of and accessibility to channels and void volume within an absorbent structure may in large part be a function of the gel bed permeability (GBP) under load of the superabsorbent material in the structure. A higher GBP under load indicates a higher ability to maintain open channels within the absorbent structure as the superabsorbent material swells under loads such as those encountered during use.
There is a need, therefore, for absorbent structures incorporating absorbent materials which have a relatively high absorbency and an enhanced free swell gel bed permeability (GBP) and gel bed permeability under load.